Can U.S. Hit Zero Risk for Ebola? Not with Africa Outbreak, CDC Says

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Oct. 3, 2014, 9:29 AM GMT / Updated Oct. 3, 2014, 9:29 AM GMT

How did someone infected with Ebola ever get into the United States in the first place?

Health officials had predicted it, and even planned for it. But now that a patient has been diagnosed with Ebola on U.S. soil, and wasn’t brought here in a special jet with a sealed isolation pod, Americans are clamoring for answers.

As long as a disease is circulating anywhere, the potential is for it to spread everywhere. Health officials say it over and over again — any disease is just a flight away from anywhere else. Experts at the World Health Organization and the Centers for Disease Control and Prevention know that well.

But the American public is being hit in the face with it, and many are stunned.

Dr. Thomas Frieden, the CDC director, says some of the public's demands are unrealistic.

“Can we make the risk zero?” he asked at a news conference Thursday. “And I think that is ultimately what everybody is asking. The bottom line is, the plain truth is that we can’t make the risk zero while there’s an outbreak in West Africa.”

People don’t always tell the truth, and they may not know either, so officials also take the temperatures of travelers as they leave affected countires. Frieden says paperwork shows Duncan was screened with an approved thermometer. “The individual did not have a fever when he left,” Frieden said.

Duncan did not get sick on the plane — air crew are trained to look for that — and he wasn’t sick when he landed in Dallas Sept. 20. By all accounts, Duncan did not start to feel ill until Sept. 24. And that fits with what is known about Ebola — people do not start to show symptoms until about eight to 10 days after they’ve been infected, and sometimes longer.

“We have already pulled people off planes or off lines to enter planes,” Frieden said. He said in September, more than a dozen people were removed and screened.

Why not stop travel from all affected countries until the outbreak is under control?

WHO recommends against that and has in fact chided airlines that have suspended flights. It’s impossible to completely close off a country, for one thing. People will find ways in and out.

And it could make the epidemic worse if aid and aid workers cannot get in to help, or if they are reluctant to come if they fear they cannot get back home.

“The best way to protect ourselves is not to seal off these countries but to provide the kinds of services so the disease is contained there. The only way to get to zero risk is to stop it there,” Frieden said.

Why can’t people be better screened when they arrive in the U.S.?

For one thing, millions of people fly into the country every year. It would create near-impossible bottlenecks at airports. During the SARS outbreak in 2003, when 8,000 people were infected with severe acute respiratory syndrome and nearly 800 died of it, Singapore and some other countries tried setting up thermal scanners to detect travelers with fever.

It didn’t work, WHO determined. And such a system wouldn’t have detected Duncan, who did not become ill until four days after he arrived. Diseases have incubation periods, and all the screening in the world won’t detect infection in people who don’t have symptoms yet. That includes blood tests — even if officials were inclined to or had the resources to test all 15,000 travelers who come from West Africa every year. People often test negative early on in Ebola infection — even after they have a fever.

“The only way to get to zero risk is to stop it there.”

Frieden says Americans really don’t need to worry about Ebola, anyway. He says even if people bring it in, good hospitals and infection control will prevent its spread. “We remain confident that we can contain any spread of Ebola within the United States,” he said.

That's even with a hospital error that sent Duncan away for two days during which he was sick and potentially exposing family member, including children, to the virus.

If Duncan infected someone else, the contact tracing now underway in Dallas will find them and get them isolated before they can infect someone else, CDC says.

WHO, the CDC, governments and non-profit groups are working to bring the Ebola epidemic under control. It's sickened more than 7,000 people and killed more than half of them, and WHO predicts 20,000 cases or more by November. Even under a best-case scenario, numbers of new infections won't start to fall until January, CDC predicts.

“It is not impossible that we will have other individuals come into the country and then be diagnosed with Ebola,” Frieden said.